Polymerization of 1,1-disubstituted alkene compounds are typically performed in bulk state, and frequently in situ, such as when monomer is placed between two substrates to be adhered. The resulting polymerization process may be difficult to control resulting in variable performance or mechanical properties. For example, the polymerization process may be characterized by one or more spikes in temperature during the polymerization process, such as by an increase in temperature of about 15° C. or more, about 30° C. or more, or even about 45° C. or more (e.g., during a polymerization reaction). Such an increase in temperature may occur in a short time period (e.g., less than 10 minutes, less than 3 minutes, or even less than 1 minute). Typically, the resulting polymer may be characterized by one or more of the following: a generally high level of branching, a high polydispersity index, a high concentration of non-polymer reaction products, a high concentration of monomers and/or oligomers, or a generally high viscosity. For example, when polymerized in bulk, the resulting polymer may have a high viscosity that makes further processing, handling, or polymerization difficult.
As used herein, bulk polymerization refers to the polymerization of a polymerizable composition including one or more monomers where the concentration of the one or more monomers is about 80 weight percent or more, preferably about 90 weight percent or more (e.g., about 100 weight percent), based on the total weight of the compounds in the polymerizable composition that are liquid at room temperature. These polymerizations typically also require an input of energy either in the form of heat or radiation to initiate polymerization.
Free radical polymerization of dialkyl methylene malonate monomers using heat, UV light and peroxide is described in U.S. Pat. Nos. 2,330,033 and 2,403,791, both incorporated herein by reference. In these patents, the monomer was prepared using traditional methods which results in low purity monomer. The polymer examples in these patents are all prepared via bulk polymerization. One would therefore not expect to be able to control polymer properties, such as molecular weight and molecular weight distribution.
However, while earlier methods for producing certain methylene malonates have been known in the art, these prior methods suffer significant deficiencies that preclude their use in obtaining commercially viable monomers. Such deficiencies include unwanted polymerization of the monomers during synthesis (e.g., formation of polymers or oligomers or alternative complexes), formation of undesirable side products (e.g., ketals or other latent acid-forming species which impede rapid polymerization), degradation of the product, insufficient and/or low yields, and ineffective and/or poorly functioning monomer product (e.g., poor adhesive characteristics, stability, or other functional characteristics), among other problems. The overall poorer yield, quality, and chemical performance of the monomer products formed by prior methods have impinged on their practical use in the production of the above commercial and industrial products.
Polymerization of 1,1-disubstituted alkene compounds using anionic polymerization processes are useful in the bulk polymerization of 1,1-disubstituted alkene compounds and processes which can operate at or near ambient conditions (starting conditions) have been disclosed. Such anionic bulk polymerizations may be initiated using a wide range of initiators, and may even be initiated by contact with certain substrates. Other bulk polymerization reactions may be initiated by UV light. However, as discussed above, the bulk polymerization may limit the ability to control the structure of the polymer molecules and/or to be able to easily handle the resulting polymer composition or product. These difficulties in bulk polymerization may be particularly pronounced when manufacturing large quantities of polymer, where heat transport issues may occur, especially when there may be shear heat generated by the flow of the high viscosity polymer and/or heat emitted due to the inherent exothermic nature of the polymerization.
Bulk polymerization of 1,1-disubstituted alkene compounds also present a challenge when attempting to control the structure of the polymer by including one or more comonomers. For example, the high viscosity of the intermediate polymer may present difficulties in preparing a block copolymer (such as by sequential addition of a first monomer system followed by a second monomer system into a reaction vessel). Other problems may arise when attempting to control the structure of a random copolymer, where the reaction rates of the different monomers differ so that the monomers are not uniformly distributed along the length of the polymer molecular. For example, copolymers including one or more 1,1-disubstituted alkene compounds prepared by bulk polymerization are typically expected to have a generally blocky sequence distribution and/or result in polymer molecules having a broad distribution of monomer compositions. As used herein, a copolymer having a generally blocky sequence distribution of monomers may be characterized as having a blockiness index of about 0.7 or less, about 0.6 or less or about 0.5 or less, or about 0.4 or less.
Although solution polymerization processes have been employed in free radical polymerization process to better control the polymer architecture, such processes have not generally been employed in anionic polymerization of 1,1-disubstituted alkenes.
When a solution polymerization system is employed with anionic polymerization methods, sub-ambient temperatures (e.g., less than 10° C., less than 0° C., or less than −20° C. are typically required to control the reaction. As such, in solution polymerization systems it may be necessary to use a cooling systems and/or insulation for achieving and/or maintain such a low reaction temperature.
Additional difficulties in polymerization of 1,1-disubstituted alkene compounds arise from the possibility of the anionic group of the growing polymer reacting with an acid thereby terminating the reaction. Therefore, one would avoid using an acid in polymerizing 1,1-disubstituted alkene compounds using anionic polymerization.
Prior attempts at anionic polymerization processes (e.g., bulk polymerization processes) for 1,1-disubstituted alkene compounds generally have had one or more of the following drawbacks: (1) requirement that the systems have low polymer concentrations; (2) have lacked reproducibility for controlling molecular weight distribution, or (3) have undesirable reactant by-products.
There is a need for polymerization methods, systems, and resulting polymer compositions or products that allow for improved control of one or more of the following properties of a polymer containing one or more 1,1-disubstituted alkene compounds: the weight average molecular weight, the number average molecular weight, the polydispersity index, the zero-shear viscosity of the polymer (e.g., at one or more temperatures of at least about 20° C. above the melting temperature of the polymer), the viscosity of the polymer system (e.g., the bulk polymer or the polymer solution) at room temperature, the sequence distribution of monomers in a random copolymer, or having at least two different polymer blocks covalently bonded (e.g., each containing one or more 1,1-disubstituted alkene compounds). There is also a need for polymerization process which can be scaled-up (e.g., to a reactor of about 20 liters or more, or having a throughput of about 10 kg of polymer per hour or more. There is also a need for processes that result in a solution containing the polymer. Such solutions may be useful for applications such as paints, coatings, finishes, polishes, and adhesives. For example, there may be a need for process and polymer systems that result in a solution having a controlled viscosity and/or polymer concentration.